.btn_b {
	border: none;
	padding: 5px 20px;
	text-align: center;
	text-decoration: none;
	display: inline-block;
	font-size: 16px;
	margin: 4px 2px;
	cursor: pointer;
}

.btn_error {
	background-color: #f44336;
	color: black;
}

.btn_primary {
	background-color: #e7e7e7;
	/* background-color: #008CBA;  blue
		background-color: #f44336; 红色
		background-color: #555555; black
		background-color: #4CAF50; green */
	color: black;
}
.btn_primary:hover{
	background-color: #555555;
	color: black;
}

